The literature specifies highly varying methods for the construction of three-dimensional objects of “light-hardening” photopolymers, cf. “Automated Fabrication—Improving Productivity in Manufacturing” by Marshall Burns, 1993 (ISBN 0-13-119462-3).
Known possibilities are, inter alia, the exposure by    a) multimedia projector    b) LC display (reflexive, transmissive)    c) LED or laser diode line (which is moved over the area orthogonally to the line)    d) light valve technology (MEMS).
These methods are described in the following patents:
US Patent US005247180A “Stereolithographic Apparatus and Method of use” by Texas Instruments Inc., September 1993;
US Patent US005980813A “Rapid Prototyping using multiple materials” by SRI International, November 1999;
Utility model publication DE G 93 19 405.6 “Device for the production of a three-dimensional object (model) according to the principle of photo solidification” by the Research Center Informatics at the University of Karlsruhe, December 1993;
According to a similar method, the utility model publication DE 299 11 122 U1 “Device for producing a three-dimensional object”, DeltaMed inter alia, June 1999 describes an application for the generation of micro-technical, three-dimensional components.
EP 1250997A (=US2002155189A) “Device for producing a three-dimensional object” by Envision Technologies GmbH, April 2002.
German Patent DE69909136T “Rapid Prototyping Device and Rapid Prototyping Method”, July 2003 (equivalent: European Patent EP 1156922 “Rapid Prototyping Apparatus and Method of Rapid Prototyping”, August 2003) of DICON AS Lystrup, Denmark.
WO 01/00390 A by HAP, Sitec Industrietechnologie and DELTAMED Medizinprodukte GmbH.
WO 2005/110722 A of Envisiontec GmbH.
With laser-based systems for photo-polymerization, the light output in the exposure point is provided by the energy setting of the laser beam, whereby the hardening depth of the solidifiable material, such as the photopolymer, can be controlled in that point.
For selective hardening, the laser beam is scanned over the cross-sectional area to be correspondingly hardened. The contours of the cross-sectional area to be hardened can be scanned by the laser beam as a curve.
A cross-sectional area is typically exposed at once with systems for photo-polymerization based on mask projection by means of projection systems, especially with the SLM technology. The white areas of the projected image harden the solidifiable material (normally a photopolymer); the black areas do not. The contours of the cross-sectional area to be hardened can only be presented in rasters; the resolution depends on the number of image points or, respectively, pixels and on the size of the projected image.
With the above mentioned WO 01/00390 A, the intensity of beams is controlled by controlling the permeability of the mask, wherein the intensity may be controlled via the selection of gray levels of a transmission LCD. An allocation by different intensities is, however, performed with respect to a layer only depending on whether solidified regions are underneath or not. There is no mentioning in WO 01/00390 of an adjustment and/or a control of an energy input in a voxel matrix as according to the present invention. The present invention deals with resolution and fine adjustment in a voxel matrix; while grey level gradation depending on whether an underneath hardened layer is absent or present for connection is not required in the present invention.
In WO 2005/110722 A, a multiple exposure is carried out on the subpixel level for improving the resolution along the outside and inside contours of the cross-sectional areas of the object to be generated, said exposure consisting of a sequence of a plurality of images offset on the subpixel level in the image/building plane, wherein a separate mask/bitmap is generated for every offset image. A gray level adjustment is taken into account for the contour pixels obtained by the subpixel offset. There is neither any mentioning in WO 2005/110722 A of an adjustment and/or a control of an energy input in a voxel matrix as according to the present invention.
Neither WO 01/00390 A nor WO 2005/110722 show how the resolution and the fine adjustment in the image plane can be improved, and how native inhomogeneities of the light source can be balanced better.